A kind of exchange micro-current is traced to the source device and method
Technical field
The present invention relates to electricity field of measuring techniques, trace to the source device and method more particularly to a kind of exchange micro-current.
Background technique
The minimum range of existing high accuracy digital multimeter measurement alternating current is 100 μ A, needs the school since 10 μ A
It is quasi-;High accuracy Multifunctional standard source automatic can export 10 μ A exchange micro-current, it is also desirable to the standard volume of output is determined by calibration
Value;But currently without the standard of calibration 1mA exchange micro-current below, also without accurately and reliably source tracing method.
There are two types of approach for the source tracing method of alternating current at present:
First is that heat to electricity conversion method uses direct current compared with carrying out by the virtual value of alternating current with standard direct current stream
The magnitude of stream determines the magnitude of alternating current.In the prior art, the critical equipment that alternating current and DC current compare is realized
It is the thermoelectric converter using thermocouple as core.The working principle of thermocouple is to be based on Seebeck effect, i.e., will be two different
Conductor both ends connect forming circuit, if two tie point temperature are different, form the electricity that pyroelectric effect generates in the loop
Thermoelectric converter can be made using this principle in kinetic potential, also referred to as Seebeck electromotive force.Thermoelectric converter is by heater strip and heat
Galvanic couple composition can generate Joule heat on heater strip and heat to thermocouple, thermocouple is made to generate heat by electric current by heater strip
Potential, thermoelectrical potential size depend on thermocouple material and the electric current by heater strip, and thermoelectric converter can be generated by DC current
Thermoelectrical potential can also generate thermoelectrical potential by alternating current, and in the good situation of heater strip frequency response, DC current is exchanged with equivalent
Current effective value pyroelectric effect having the same, exports identical thermoelectrical potential, thus can realize alternating current and DC current
Compare, so that the magnitude of realization DC current determines the magnitude of alternating current.In the prior art, using thermoelectric converter as
Ac and dc current converted measurement device realizes the standard set-up of analog ac and dc current converted measurement, but analog friendship is straight
Galvanic electricity stream converted measurement the problem is that input current will in 10mA or more, the pyroelectric effect that generates less than 10mA electric current it is defeated
Voltage is too small out, poor signal to noise, required accuracy is not achieved, therefore heat to electricity conversion method not can solve 1mA or less and exchange micro- electricity
The problem of tracing to the source of stream.
Second is that Current Voltage transformation approach: the measurement of electric current is usually that divertor is used to be converted to tested current signal
Voltage signal measures, i.e., the magnitude of divertor it is known that the instrument accuracy grade of measurement voltage it is known that shunt resistance can be passed through
The ratio of voltage drop and resistance on device converts to obtain the magnitude of tested electric current, therefore the measurement of alternating current just needs alternating current
Hinder current divider and A.C. voltmeter.AC resistance current divider be frequency error it is small, can be by the resistor of rated current, wherein really
Its fixed frequency error is current technical problem, at home never effective solution, in the world only Britain NPL and Germany
PTB is capable of providing the calibration service of AC resistance.And the input impedance of A.C. voltmeter is usually in 1M Ω, when measuring 10 μ A's
When exchanging micro-current, the divertor of 100k Ω is needed, at this moment due to the shunting function of the input impedance of A.C. voltmeter, is made
Measurement error reaches 10%, with 10-5To 10-4The demand of tracing to the source of magnitude differs greatly.
By being analyzed above it is found that exchanging tracing to the source for micro-current is the problem of international electrical metering field, at present in the world
High accuracy there is no to exchange micro-current calibrator product.
Summary of the invention
The present invention proposes a kind of source tracing method and device for exchanging micro-current, uses according to defect of the existing technology
Low noise broadband amplifiers combines the equivalent AC resistance to be formed with AC resistance current divider --- and exchange micro-current calibrator leads to
The frequency error that Calculable resistor determines AC resistance current divider is crossed, signal is realized by low noise broadband amplifiers
Amplification and impedance transformation, overcome voltage that current divider resistance is converted out it is small it is low with A.C. voltmeter input impedance caused by measurement
The big problem of uncertainty, solving the problems, such as exchange micro-current 1mA to 10 μ A, (50Hz traces to the source to 10kHz's), and measurement is uncertain
Degree reaches 10-5To 10-4Magnitude.
The technical scheme is that
1. a kind of device of tracing to the source for exchanging micro-current, which is characterized in that including with by AC resistance current divider and low noise
Sound broadband amplifiers combines the equivalent AC resistance to be formed --- exchange micro-current calibrator, to the exchange micro-current calibrator
The tested exchange micro-current of input measures the output voltage of the exchange micro-current calibrator by high accuracy A.C. voltmeter,
It can convert to obtain the tested magnitude for exchanging micro-current with the ratio of equivalent AC resistance magnitude by the alternating voltage magnitude measured;Institute
It states AC resistance current divider to be calibrated by Calculable resistor, the low noise broadband amplifiers passes through times magnification
Number verifying device is verified, and the A.C. voltmeter is calibrated by exchange standard voltage source.
2. Calculable resistor is calibrated AC resistance current divider, the exchange by AC resistance transfer device
Resistance transfer device is that sensitivity and resolving power are not less than 10-6The AC bridge of magnitude, can by alternating current-direct current difference by AC bridge
It calculates resistance to be compared at different frequencies with AC resistance current divider, obtains the frequency error of AC resistance current divider.
3. the Calculable resistor is coaxial type Calculable resistor, including coaxial interior metallic sheath
Cylinder and outer metal sleeve have single straight linear resistive silk on the central axis of the interior metal sleeve, from the resistance wire
Extracted current positive terminal lead-out wire and positive polarity end lead-out wire, from extracted current negative pole end on the interior metal sleeve front end face
Lead-out wire, from extraction voltage negative pole end lead-out wire on the outer metal sleeve front end face.
4. the low noise broadband amplifiers is made of devices such as low noise wideband operational amplifier and noninductive resistances, frequency
Rate range reaches 10 in 50Hz to 10kHz, the accuracy of amplification factor-5Magnitude.
5. the low noise broadband amplifiers combines the equivalent AC resistance to be formed with AC resistance current divider --- exchange
Micro-current calibrator, output impedance go to zero.
6. the amplification factor verifying device is by inputting known standard voltage signal, measurement to low noise broadband amplifiers
Its output voltage signal, the amplification factor error varying with frequency obtained with the ratio of input voltage and output voltage, with verifying
The frequency response of amplifier.
7. a kind of exchange micro-current calibrator, which is characterized in that including AC resistance current divider, the AC resistance is shunted
Device combines to form equivalent AC resistance with low noise broadband amplifiers;The low noise broadband amplifiers is transported using low noise wideband
It calculates the devices such as amplifier and noninductive resistance to be made, frequency range reaches 10 in 50Hz to 10kHz, the accuracy of amplification factor-5Amount
Grade;The low noise broadband amplifiers combines the equivalent AC resistance to be formed with AC resistance current divider, and output impedance tends to
Zero.
8. a kind of source tracing method for exchanging micro-current, which is characterized in that use low noise broadband amplifiers and AC resistance
Current divider combines to form equivalent AC resistance, and tested current signal is converted to voltage signal, passes through high accuracy alternating voltage
Table measures the output voltage of equivalent AC resistance, converts to obtain by test cross by the ratio of the voltage value and equivalent AC resistance that measure
Flow the magnitude of micro-current.
9. the described method comprises the following steps:
1) it calibrates AC resistance current divider: being not less than 10 by sensitivity and resolving power-6The AC bridge of magnitude is straight with handing over
Stream difference can calculate resistance calibration AC resistance current divider, obtain the frequency error of AC resistance current divider.
2) develop wideband AC amplifier: the low noise broadband amplifiers is using low noise operational amplifier and without electrification
The accurate devices such as resistance are made, and the accuracy of amplification factor must reach 10-5Magnitude.
3) frequency response of low noise broadband amplifiers is verified: to the standard electric of the input different frequency of low noise broadband amplifiers
Pressure, measures its output voltage, with the ratio of input voltage and output voltage, obtains the frequency error of amplifier.
5) to low noise broadband amplifiers combined with AC resistance current divider to be formed equivalent AC resistance input quilt
Test cross stream micro-current, and the output voltage of high accuracy A.C. voltmeter measurement equivalent AC resistance is accessed, by the voltage measured
Value converts to obtain the tested magnitude for exchanging micro-current with the ratio of equivalent AC resistance.
10. in the step 1), the step of calibrating AC resistance current divider, is: poor by measuring and calculating alternating current-direct current first
The distribution parameter that resistance can be calculated obtains the magnitude of Calculable resistor under different frequency;It is realized by AC bridge
Tested AC resistance current divider determines AC resistance current divider at different frequencies compared with Calculable resistor
Resistance value obtains the frequency error of AC resistance current divider.
Technical effect of the invention:
A kind of device and method of tracing to the source exchanging micro-current proposed by the present invention, using by AC resistance current divider and low noise
Sound broadband amplifiers combines the equivalent AC resistance to be formed --- exchange micro-current calibrator, to exchange micro-current calibrator input
Tested exchange micro-current, measures its output voltage by high accuracy A.C. voltmeter, by the alternating voltage magnitude measured and waits
Effect AC resistance magnitude can convert to obtain the magnitude of tested exchange micro-current.Alternating current is determined by Calculable resistor
The frequency error for hindering current divider realizes signal amplification and impedance transformation, and low noise wideband by low noise broadband amplifiers
Amplifier is verified device by amplification factor and is verified, and A.C. voltmeter is calibrated by exchange standard voltage source, is overcome
The voltage that current divider resistance is converted out it is small it is low with A.C. voltmeter input impedance caused by the big problem of uncertainty of measurement, solve
(problem of tracing to the source of 50Hz to 10kHz), uncertainty of measurement reach 10- by exchange micro-current 1mA to 10 μ A5To 10-4Magnitude.
Detailed description of the invention
Fig. 1 is the schematic illustration of the device of tracing to the source of exchange micro-current of the invention.
Fig. 2 is the structural schematic diagram of the computable alternating current-direct current difference resistance in Fig. 1.
Appended drawing reference lists as follows: 1- resistance wire, metal sleeve in 2-, 3- housing metal cylinder.
Specific embodiment
The embodiment of the present invention is described in further detail below in conjunction with attached drawing.
As shown in Figure 1, being the schematic illustration of the device of tracing to the source of exchange micro-current of the invention.A kind of exchange micro-current
It traces to the source device, including combining the equivalent AC resistance to be formed with AC resistance current divider with low noise broadband amplifiers --- friendship
Micro-current calibrator is flowed, tested exchange micro-current is inputted to the exchange micro-current calibrator, passes through high accuracy alternating voltage
Table measures the output voltage of the exchange micro-current calibrator, is converted by the ratio of the voltage value and equivalent AC resistance that measure
To the magnitude of tested exchange micro-current;Wherein, AC resistance current divider is calibrated by Calculable resistor, low noise
Sound broadband amplifiers is verified device by amplification factor and is verified, and A.C. voltmeter is calibrated by exchange standard voltage source.
Calculable resistor is developed first, obtains the resistance-frequency error of Calculable resistor.It is former
Reason is: under exchange status, parasitic inductance present in AC resistance device and parasitic capacitance and various added losses are main
It is related with the electromagnetic environment of the shape of resistance device, position and surrounding, therefore, develop the resistor of regular geometry, so that it may
Its parasitic inductance and parasitic capacitance and various added losses are calculated, to obtain the reality of AC resistance magnitude and D.C. resistance
Portion's difference and imaginary part error (time constant), thus can export its AC resistance magnitude from the D.C. resistance magnitude that can be traced to the source, make
AC resistance is also provided with traceability.The resistor of this special development is known as " Calculable resistor ".It is straight due to handing over
The key that stream difference can calculate resistance development is to obtain determining distribution parameter magnitude by theory analysis and actual measurement, determine
The influence of the impedance magnitude of frequency variation, computation model are directly related to the accurate of measurement result.For ease of calculation and analyze,
By the analysis to parasitic inductance, parasitic capacitance and skin effect, the present invention is using coaxial type Calculable resistor
Model, as shown in Figure 2.The coaxial type Calculable resistor, including coaxial interior metal sleeve 2 and outer metal sleeve
3, there is on the central axis of interior metal sleeve 2 single straight linear resistive silk 1, drawn from extracted current positive terminal on resistance wire 1
Line I+ and positive polarity end lead-out wire V+, from extracted current negative pole end lead-out wire I- on interior 2 front end face of metal sleeve, from outer metal
Extraction voltage negative pole end lead-out wire V- on 3 front end face of sleeve.The resistance of coaxial type structure is divided into three parts: in resistance wire
It is derived respectively inside part and metallic cylinder between portion, resistance wire and metallic cylinder.It is calculated in resistance wire electric
The interior self-induction of external inductance between sense, resistance wire and metallic cylinder, metallic cylinder, and then obtain total parasitic inductance;It is calculated
Capacitor C between resistance wire and metallic cylinder surface;The frequency draft of skin effect generation is calculated;And then according to different frequencies
The real part error and imaginary part error that coaxial type Calculable resistor is generated with frequency variation is calculated in rate.
Secondly, Calculable resistor is calibrated into AC resistance current divider by AC resistance transfer device, it is described
AC resistance transfer device is that sensitivity and resolving power are not less than 10-6The AC bridge of magnitude, by AC bridge by alternating current-direct current
Difference can calculate resistance and be compared at different frequencies with AC resistance current divider, obtain AC resistance current divider in different frequency
Under resistance value, i.e. the frequency error of AC resistance current divider.
For the influence for reducing input impedance when AC resistance current divider accesses A.C. voltmeter, the present invention puts wideband exchange
For big device in conjunction with AC resistance current divider, the equivalent resistance of realization has low output impedance, the output impedance of present apparatus embodiment
It goes to zero.
The low noise broadband amplifiers, is made of low noise wideband operational amplifier and noninductive resistance, manufactured low
The accuracy of noise broadband amplifiers amplification factor reaches 10-5Magnitude;Frequency range is in 50Hz to 10kHz.
For the amplification factor frequency error varying with frequency for verifying low noise broadband amplifiers, verified using amplification factor
Device measures its output voltage signal, uses input voltage by inputting known standard voltage signal to low noise broadband amplifiers
And the amplification factor error varying with frequency that the ratio of output voltage obtains, to verify the frequency response of amplifier.
A kind of exchange micro-current calibrator is made in low noise broadband amplifiers by the present invention in conjunction with AC resistance current divider,
Including AC resistance current divider, the AC resistance current divider combines to form equivalent AC resistance with low noise broadband amplifiers;
Wherein, low noise broadband amplifiers is made of devices such as low noise wideband operational amplifier and noninductive resistances, and frequency range exists
The accuracy of 50Hz to 10kHz, amplification factor reach 10-5Magnitude;Low noise broadband amplifiers is combined with AC resistance current divider
The equivalent AC resistance of formation, output impedance go to zero.
It is a kind of exchange micro-current source tracing method be that shape is combined with AC resistance current divider using low noise broadband amplifiers
At equivalent AC resistance --- exchange micro-current calibrator, after the exchange micro-current calibrator is passed through tested exchange micro-current,
Tested current signal is converted into voltage signal, the output electricity of equivalent AC resistance is measured by high accuracy A.C. voltmeter
Pressure is converted to obtain the tested magnitude for exchanging micro-current with the ratio of equivalent AC resistance by the voltage value measured.
The following steps are included:
1) it calibrates AC resistance current divider: being not less than 10 by sensitivity and resolving power-6The AC bridge of magnitude is straight with handing over
Stream difference can calculate resistance calibration AC resistance current divider, obtain the frequency error of AC resistance current divider.
2) develop wideband AC amplifier: the low noise broadband amplifiers is using low noise operational amplifier and without electrification
The accurate devices such as resistance are made, and the accuracy of amplification factor must reach 10-5Magnitude.
3) frequency response of low noise broadband amplifiers is verified: to the standard electric of the input different frequency of low noise broadband amplifiers
Pressure, measures its output voltage, with the ratio of input voltage and output voltage, obtains the frequency error of amplifier.
5) to low noise broadband amplifiers combined with AC resistance current divider to be formed equivalent AC resistance input quilt
Test cross stream micro-current, and the output voltage of high accuracy A.C. voltmeter measurement equivalent AC resistance is accessed, by the voltage measured
Value converts to obtain the tested magnitude for exchanging micro-current with the ratio of equivalent AC resistance.
Wherein, in step 1), calibrate AC resistance current divider the step of be: first by measure and calculate alternating current-direct current difference can
The distribution parameter for calculating resistance, obtains the magnitude of Calculable resistor under different frequency;Quilt is realized by AC bridge
Test cross leakage resistance current divider determines the electricity of AC resistance current divider at different frequencies compared with Calculable resistor
Resistance value obtains the frequency error of AC resistance current divider.